Enhanced CO2 injection and hydrate conversion in unsealed submarine sediments for CO2 hydrate sequestration by CO2-H2O emulsion injection
Abstract
CO2 hydrate provides an important alternative solution for CO2 geological sequestration. However, fingering flow of liquid CO2 and hydrate membrane effect can severely restrict flowing CO2 conversion to hydrate. Here we report an enhanced CO2 hydrate sequestration method via CO2-H2O emulsion injection, and its effectiveness has been proven in a three-dimensional system. Compared to liquid injection, emulsion injection demonstrated higher displacement efficiency of pore water and larger sweep area, finally increasing CO2 sequestration density by 142?%. The highly dispersed CO2 micro-droplets significantly increase CO2-H2O contact capability and weakens the hydrate membrane effect, thereby greatly increasing the rate and quantity of hydrate conversion. For different water contents, the highest CO2 sequestration density of 148?kg/m3 is achieved at 40?% water content, with hydrated CO2 accounting for 71.45?%. The excellent performance of CO2-H2O emulsion provides a green and high-efficient approach to CO2 hydrate sequestration.